/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.giraph.utils;

import org.apache.hadoop.io.DoubleWritable;

import java.util.Iterator;

/**
 * A helper class for math related operations with writables
 */
public class MathUtils {

  /**
   * Utility classes cannot be instantiated
   */
  private MathUtils() {
  }

  /**
   * Sums up a sequence of double values
   * @param values double values
   * @return sum of double values
   */
  public static double sum(Iterable<DoubleWritable> values) {
    return sum(values.iterator());
  }

  /**
   * Sums up a sequence of double values
   * @param values double values
   * @return sum of double values
   */
  public static double sum(Iterator<DoubleWritable> values) {
    double sum = 0;
    while (values.hasNext()) {
      sum += values.next().get();
    }
    return sum;
  }
}
